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Extraordinary elongation - Tanystropheids

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A selection of archosauromorph reptiles known as tanystropheids, to scale.
Fossils from the Triassic period reveal an amazing range of weird and wonderful creatures. The devastating extinction at the end of the Permian (also known as the Great Dying) wiped the slate virtually clean, removing 57% of all biological families, 81% of marine life and 70% of terrestrial vertebrates. Vertebrates on land struggled to recover, taking about 30 million years before the diversity was back to pre-extinction levels. Some surviving species which were previously rare, suddenly found new opportunities and became more numerous. Sauropsid reptiles were particularly diverse in shape and form during the Triassic (see Sea-snoots - Thalattosaurs, Copy-crocs 1 - Phytosaurs, King fish lizards - Shastasaurids, Armoured shellfish snackers - Placodonts, Oddball beaky pig lizards - Rhynchosaurs, Crimson Crocs - Erythrosuchids, and Monkey-lizards - Drepanosaurs). And that doesn't include the first dinosaurs and pterosaurs! One particular group of oddball archosauromorphs, the tanystropheids, were notable for their long necks.
The coastline of the shallow Tethys Sea was home to most of tanystropheids including the iconic (and ludicrously) long necked Tanystropheus. Roughly half of it's entire length was composed of the stiffened neck. Possibly not surprisingly when first discovered the stretched out cervical vertebrae were so long that they were thought to be the wing bones of a pterosaur. In addition to the 5 metre long individuals were much smaller ones (1.5 metre long) which were thought to be juveniles. Presence of growth rings showed the smaller ones were actually adults of a dwarf species, T. longobardicus that lived alongside the much larger T. hydroides. Niche partitioning could be seen in the skulls with the long teeth of hydroides ideal for hunting fish while the cusped teeth of longobardicus adapted for crushing invertebrates. Finally the nostrils were dorsally located indicative of aquatic lifestyle, and the long neck probably allowed breathing and hunting with minimal movement from the shallow seabed. Neither species were fast or agile swimmers, unlike the more distantly related Dinocephalosaurus. Adaptations such as poorly ossified paddle-like limbs, dorsally located eyes and live birth reveal Dinocephalosaurus to be a full-time aquatic species. It was one of the few viviparous archosauromorphs aside from a lineage of marine crocodylomorphs (see All at sea - Metriorhynchids). An extraordinary find of nearly 100 specimens of a smaller aquatic species, Tanytrachelos have been found in great abundance in the sediment of an ancient lake in Eastern USA. Many of the specimens were fully articulated individuals and some also included soft tissue. Interestingly it was an unusual example of a freshwater tanystropheid.
Not all tanystropheids were aquatic reptiles. One of the better known terrestrial forms was Macrocnemus, which had a lightweight body, modest length of neck and gracile limbs. Elessaurus was an earlier species, a significant find from Brazil indicating that early tanystropheids probably had a much wider range into Southern Pangaea. If tanystropheids weren't odd enough, some taxonomic studies place the gliding sharovipterygids (see Up in the air - Gliding reptiles) as a closely related group.
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DaBair's avatar

Tanystropheus was definitely one of the weirdest prehistoric reptiles - and it's one of my favorites for that reason.

artbyjrc's avatar

Tanystropheus is in a pretty small club of being unique in appearance/behaviour.

kirakuru-x's avatar

I thought all tanystropheid species were marine reptiles.

artbyjrc's avatar

Nope. Bit of a mixture. Gets even more complicated if I had added the gliding sharoviptergyids as well!

WDGHK's avatar

I can’t avoid talking about its appearance in Chased by Sea Monsters, where, outside of being portrayed as a marine reptile, it was also infamously depicted as being capable of caudal autotomy, that is, being able to break off its tail when attacked by a predator, like some modern lizards. That idea was actually proposed by German paleontologist Rupert Wild, who was heavily involved in research on Tanystropheus during the 20th century. Notably, he thought that Tanystropheus was closely related to lizards, with it being part of the lepidosauromorphs. But several subsequent studies placed it and other “protosaurs” as archosauromorphs not long after Wild’s initial 1973 classification. In a 1975 paper, Wild cited one specimen from Ticino as allegedly sporting an autotomized tail, with the break-off point being at the 14th caudal vertebra, with textures on the vertebrae supposedly supporting that. However, subsequent studies have all dismissed Wild’s interpretation.

artbyjrc's avatar

Although I was familiar with the seen in CbSM, I wasn't awrae that it had been historically suggested as an idea. Seems remarkable to think that with odd proportions of Tanystropheus, that it might be capable of losing other parts of the body.

WDGHK's avatar

Probably because it COULDN’T do that. Hence why future studies all disputed that idea by reexamining that one Ticino specimen. By all accounts, Wild’s interpretation was mistaken and it also hinged a lot on his belief that Tany was closely related to squamates, which no future studies have supported. I merely brought it up because a lot of people (including you it seens) seem to be under the impression that CBSM just outright fabricated that, when they didn’t. Most of the creative liberties in the WW had some basis on science, even if they often fell back on dubious sources of evidence such as fragmentary fossils and controversial/dated theories.

artbyjrc's avatar

To clarify my previous comment, I meant seems remarkable that people thought it was possible (I always thought it was wild speculation). It just seems like an unlikely strategy for an animal with such unbalanced proportions to be further compromised.

It does seem that the WW... series did like to use 'facts' to back up claims, even if they were incredibly unlikely hypothesis to begin with.

I know they are not closely related to plesiosaurs, but I just realized they were evolved convergently with plesiosaurs, seeing as a couple of them have long necks.

WDGHK's avatar

There’s a big difference though, plesiosaurs had many, many more neck vertebrae, allowing for greater (though still limited) neck flexibility. Tanystropheus, on the other hand, only had 12-13 very elongated neck vertebrae, making its neck much more ridged, more like a giraffe or azhdarchid pterosaur’s. Couple that with the likelihood that Tany was more of an amphibious animal and a capable walker, it and plesiosaurs really aren’t all that similar, sans being diapsids and the “long neck” thing.

artbyjrc's avatar

I think BigCtrain might have been referring to Dinocephalosaurus, although your argument might still stand re: neck vertebrae.

artbyjrc's avatar

Pre-empted the pleisosaurs and convergent with Triassic pistosaurs (ancestral line to plesiosaurs).

YappArtiste's avatar

Ahhh... the oddball longnecks of the Triassic. Never heard of Langobardisaurus nor knew it was another case of convergent evolution with dinosaurs.

Ta-tea-two-te-to's avatar

That bipedal Tanystropheid is certainly interesting. However, it should be noted that one of the authors of the paper that described the movement of Langobardisaurus contains David Peters.

artbyjrc's avatar

Illustration was only trying to indicate being able to stand briefly on hind legs. Similar behaviour to a standing meerkat or running for short bursts on hind legs like a basilisk. I don't believe that it moved around bipedally all the time.

Ta-tea-two-te-to's avatar

Yes, I think it could stand up at least.

Ill-Fated-Jedi's avatar

Your write-up calls them Dinocephalus, but the full name is Dinocephalosaurus. Is that a deliberate abbreviation, then? Also it looks very convergent with both nothosaurids and plesiosaurids, which is very cool from a Tanytropheid. Btw, there are fossils of trackways in Germany purported to be from Tanystropheus species that show that it lunge-hunted, floating through the water until it spotted a fish and then thrusting itself with frog kicks to use its long neck like a javelin. A very weird and inefficient hunting strategy from a coastal hunter if true, but hey that's the Triassic for you.

artbyjrc's avatar

Typo. Thanks for the pickup.

I hadn't heard of the trackways, but the purported hunting style is very interesting and unique.

Ill-Fated-Jedi's avatar

Isn't it so cool? I hope it is true, because it's so unlike anything alive today but actually does work with the admittedly extremely bizarre anatomy

artbyjrc's avatar

It's sort of like an underwater heron which couldn't bend it's neck, so using legs to thrust forward instead. Extremely odd. And yes I hope that it's true as well.

SheTheTDE's avatar

cousins of the butt wing dragons

WDGHK's avatar

Highly debatable. Protosaurs might very well be a polyphyletic group.

Olmagon's avatar

I think the drawing calling it Dinocephalosaurus is the right name rather than Dinocephalus as the text and tags calls it.

artbyjrc's avatar

Typo and I've changed it. Thanks.

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